Receiver



H. HEWEL June 9, 1942.

RECEIVER Filed Nov. 11, 193'? 2 Sheets-Sheet l June 9, 1942.

HORST HEWE'I.

mfm

ATTORNEY nte-med June 9, 1942' nom nevel, mun-menuisier, Germany, ss'- signor to Telefunken v,Gesellschaft fr Drahtlose Telegraphie m. b. corporation of Germany li., Berlin, Germany, a

Application November 11, 1931, Serial No. 173,972 In vGermany November 3, 1936 (ci. 11a-5.a)

s claims.

This invention relates to radio receivers, and in particular, to receivers adapted to receive both television and video and accompanying laudio or sound signals simultaneously.

It is customary in present day practice in television transmission to accompany the picture or video signals with sound or audio signals, each of the signals being placedon separate carriers, which carriers are separated in the frequency spectrum by a fixed frequency difference, re-

gardless of which portion of the spectrum the4 video and accompanying sound signals are positioned at. A suitable receiver for receiving both fof these transmissions under a single manual f control is described in U. S. Patent N0. 1,975,056,

the tuning process, as the frequency spectrum is being covered, the video signals are prevented from going through, the audio channel, thereby preventing receiving sound effects produced by thevideo signals. This disturbance of course, is quite great in the ordinary receiver, but by the invention lhereinafter described in detail, this deleterious feature is overcome. c l

"At the same time the invention provides for proper tuning of the audio channel so that any distortionrwhichmightarise from mistuning of this channel is overcome. Mistuning of the audio channel in the ordinary receiver gives both distorted sound outputs and poor picture reproduction because of the fixed frequency spacing between the video and audio channels. nConsequently, the invention eliminates distortion in the video channel as well as the sound channel. It is an object, therefore, of the invention to provide a simpler tuning method. for combined audio and video receivers and at the same time to provide a receiver which is free from noise during the tuning-process. c y

A furtherobject is to provide a combined audio and video receiver inwhich the video channel is blocked until the audio carrier passing throughthe video channel is automatically blocked and unblocked in accordance with the tuning of the sound channel, so that proper tuning of the sound channel gives proper tuning of the. video channel, and at the same time, prevents the video channel from getting through `the-sound channel during the tuning process.

In accordance with my invention, the detector circuit ofthe audio channel has a portionlof its energy diverted into a cut-off `control devicev which is also connected to one ofthe intermediate frequency stages of the video channel. When the .detector output is below a predetermined value, the cut-off control device biases the intermediate frequency amplifier of the' video channel below cut-oil so that no signals can pass through the video channel. When, however, the receiver is lprc'nierly tuned, the sound energy exceeds the predetermined value which actuates a relay, which may be of the electro-mechanical type or of thethermionic or gaseous discharge type,V to remove the bias which cuts of! the intermediate frequency amplifier of the video channel and thus permit the video frequency signals to vpassl through the picture reproducer. The video frequency signals are prevented from passing through the audio frequency channel by using any of the well known muter or quiet automatic volume control -circuits such as are well known in the art in the audio channel. Such circuits are disclosed for example in Farnham,y

1,919,160 issued July 18, 1933; Kock, 2,021,939 of November 26, 1935;'and Starrett, 2,023,448 of December 10, 1935.

Provision is also made to operate the cut-oit control device from the intermediate frequency amplifier of the audio channel in receivers where automatic volume control is provided by diverting energy from the detector to control the bias of the intermediate frequency amplifier.

Referring now to the drawings in which Fig. 1 shows in block diagram form a dual receiver embodying the invention;

Fig. 2 shows schematically the control device and its connection between the audio and video channels;

Fig. 3 shows, in block diagram the connection of the control device in a dual receiver where automatic volume control is provided; and

Fig. 4 shows a modification of the embodiment of the invention shown in Fig. 2, in which a gaseous discharge tube is used in the control de- A- vice; the invention will be described in detail.

Turning now to Fig. l there is shown a dual audio and video receiver comprising a radio frequency amplifier I, which ampliiies the received signals and is fed to a superheterodyne detector 3, which detector is also fed from the heterodyning oscillator 5. A single -control tuning m'eans 21 serves to simultaneously determine the frequency of the oscillator 5 and the pass-band of the radio frequency amplifier I. The output of the detector 3 is fed to an intermediate frequency amplifier 1 which is broad enough to receive both the video and audio bands of frequency. The output of this amplifier is then fed simultaneously to the audio channel'comprising the intermediate frequency amplifier 9, the sound detector I I. the amplifier I3, and the loud speaker I5, and to the video channel comprising the intermediate frequency amplifier I1, the detector I9, amplifier 2l, and the picture reproducing device 23. Connected between the detector II and the intermediate frequency amplier is the cutoff controli25, which control normally supplies cut-off bias to the first tube of the intermediate frequency amplifier I1, but when the amplitude of -thedetected current exceeds s, predetermined value, a relay is operated to remove this cutoff bias from the intermediate frequency amplifier I1 and permits the signals from the intermediate frequency amplifier 1 to pass through the video channel. f One form of the cut-off control which may be used is shown in Fig. 2. In this figure the intermediate frequency amplier 9 feeds energy through capacity coupling to a diode rectifier 33. A resistor and condenser 31 serve to filter the radio frequency components out of the detected output and the demodulated audio frequency is then passed on through the-amplifier I3 to the loud speaker I5. Connected to the audio output ofrthe detector is a variable resistance 39 convnected'in series with an electromagnetic relay 4 I Thev variable resistance 39 is used to control the amount of current flowing through the relay to determine ,its operating point. The relay armature 53 is connected serially with a battery and Ato the cathode of the first tube 41 of the interpositive voltage on the cathode of the tube 41.

Since the other side of the battery is grounded,

negative potential sufficient to cut off plate current of the tube 41. However, as the tuning of the receiver is varied sothat the audio voltage begins to rise at a predetermined value of its amplitude. the relay 4I opens removingthereby the large negative bias and permitting the tube 41 to operate withfnormal bias.

In Fig. 3. I have shown schematically in block ydiagram forml the receiver which is equipped with automatic volume control and in which the cut-off control device is connected between the intermediate frequency amplifier 9 and I1. A portion of the output of the detector II is fed back to one or more stages of intermediate frequency amplifier 9 so that the gain of the amplifier is' controlled inversely as the output of the detector. 'I'he cut-off control device is now suitably lconnectedqn the plate circuits of one of the stages in the intermediate frequency ampli- Afier in a similar fashion to that shown in Fig. 2

` and ydescribed above, so that only when the plate the grid yof tube 41 is maintainedvat a very large The electrode 63 is connected to a current limiting resistor to the detector output, while the electrode 65 is connected to ground so as to place the electrode 63 and B5 across the audio output voltage. Connected serially between the auxiliary electrode 61 and the electrode 65 is a resistor 69 and a battery 1I so pulled as to put negative voltage on the auxiliary electrode 61. A connec` tion between the electrode 61 and the resistor 69 is then brought to the grid of the first tube 41 of the intermediate frequency amplifier I'I, there-v by,impressing upon the grid a large negative voltage to render the tube 41 blocked so that no video signals vcan pass through the intermediate frequency amplifier I1. As the resistor is tuned, there is an increase in the amplitude of the detected audio output and when this value exceeds a predetermined point, a glow discharge will .take place between the electrode 63 and the point receiving both video and sound signalling energy,

a video channel, a sound channel, means to simultaneously tune both channels, and means connected from the sound channel to the video channel to render the video channel operative only when sound energy in the sound channel exceeds a predetermined value irrespective of the energy in the video channel.

2. A television receiver comprising means for l receiving both video and sound signalling energy, a video channel, a sound channel, means to simultaneously tune both channels, and means connected from the sound channel to the video channel to render the video channel operative,

4. A television receiver ycomprising'means fory receiving both video and sound energy, a video channel, a sound channel, a single means for simultaneously tuning both of said channels,I

electromagnetic means `connected fromvthe sound l e 2,285,857 4 channel to the video channelto render said video channel operative only when the sound energy in the sound channel exceeds a predetermined value irrespective of the value of video energy in the video channel.

5. A television receiver comprising means for receiving both video and sound energy. a video channel, a sound channel, single means for simultaneously tuning both of said channels, and electronic means connected from the sound channel tothe video channel to render said video channel operative only when the sound energy in the sound channel exceeds a predeterminedvalue irrespective of the value of video energy in the video channel. f

6. A television receiver comprising means for receiving both video and sound signalling energy,

a video channel, a sound channel, means to simultaneously tune both of said channels, an in-` termediate frequency amplifier in said video channel, and lmeans to render said intermediate frequency amplifier operative only when said sound energy in said sound channel exceeds a predetermined value irrespectiveof the\video energy in the video cHannel.

7. A television receiver comprising means for receiving both video and sound signalling energy,

a video channel, a sound channel, meansv to si" multaneously tune both of said channels, an inl 8. A television yreceiver comprising means for j receiving both video and sound signalling energy, a video channel, a sound channel, means to simultaneously tune both of said channels, an intermediate frequency amplifier in said video channel, andan electronic relay to render said intermediate frequency amplifier operative only when said sound energy in said sound channel exceeds a predetermined value irrespective of the video energy in the video channel, said electronic relay being connected in said sound channel. f

HORST 

